Method and device for signaling control information in carrier aggregation system

ABSTRACT

The present invention relates to a wireless communication system. More specially, the present invention relates to a method and a device which enable a terminal to transmit channel quality information, the method comprising the following steps: receiving a control channel, which includes a request for the channel quality information; generating the channel quality information on one or more specific downlink carriers from a plurality of downlink carriers after receiving the control channel; and transmitting the channel quality information through a shared channel, wherein the one or more specific downlink carriers are indicated using the caption of the request for the channel quality information or time information related to the transmission of the channel quality information.

TECHNICAL FIELD

The present invention relates to a wireless communication, and moreparticularly, to a method and apparatus for transmitting channel qualityinformation.

BACKGROUND ART

Generally, a wireless communication system is developing to diverselycover a wide range to provide such a communication service as an audiocommunication service, a data communication service and the like. Thewireless communication is a sort of a multiple access system capable ofsupporting communications with multiple users by sharing availablesystem resources (e.g., bandwidth, transmit power, etc.). For example,the multiple access system may include one of CDMA (code divisionmultiple access) system, FDMA (frequency division multiple access)system, TDMA (time division multiple access) system, OFDMA (orthogonalfrequency division multiple access) system, SC-FDMA (single carrierfrequency division multiple access) system and the like.

DISCLOSURE OF THE INVENTION Technical Tasks

One object of the present invention is to provide a method and apparatusfor efficiently performing signaling in a carrier aggregation system. Inparticular, the object of the present invention is to provide a methodand apparatus for efficiently signaling a control command for anindividual CC and a control command for all CCs in a carrier aggregationsystem. In more particular, the object of the present invention is toprovide a method and apparatus for efficiently transmitting channelquality information on a downlink in a carrier aggregation system.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a method oftransmitting channel quality information, which is transmitted by a userequipment in a wireless communication system using multiple carriers,according to one embodiment of the present invention may include thesteps of receiving a control channel including channel qualityinformation request, generating the channel quality information on atleast one specific DL carrier among a plurality of DL carriers afterreceiving the control channel, and transmitting the channel qualityinformation via a shared channel, wherein the at least one specific DLcarrier is indicated using time information related to a reception ofthe channel quality information request or a transmission of the channelquality information.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a user equipment, which is configuredto transmit channel quality information in a wireless communicationsystem using multiple carriers, according to another embodiment of thepresent invention may include an RF (radio frequency) unit and aprocessor configured to receive a control channel including channelquality information request, the processor configured to create thechannel quality information on at least one specific DL carrier among aplurality of DL carriers after receiving the control channel, theprocessor configured to transmit the channel quality information via ashared channel, wherein the at least one specific DL carrier isindicated using time information related to a reception of the channelquality information request or a transmission of the channel qualityinformation.

Preferably, the time information related to the reception of the channelquality information may include a subframe number for a base station totransmit the channel quality information request or for the userequipment to receive the channel quality information request, a systemframe number or a combination of the subframe number and the systemframe number.

Preferably, the time information related to the transmission of thechannel quality information may include a subframe number for the userequipment to transmit the channel quality information, a system framenumber or a combination of the subframe number and the system framenumber.

Preferably, an index indicating the at least one specific DL carrier maybe linked with modulo (X, Y), the X may be an index associated with thetime information, the Y may be the number of aggregated carriers, andthe modulo (X, Y) may indicate a remainder resulting from dividing the Xby the Y.

Preferably, the channel quality information may include at least one ofCQI (Channel Quality Indicator), PMI (Precoding Matrix Indicator) and RI(Rank Indicator).

Preferably, the control channel may further include carrier indicationinformation.

Preferably, the control channel may include PDCCH (Physical DownlinkControl Channel) and the shared channel may include PDSCH (PhysicalDownlink Shared Channel).

Advantageous Effects

According to embodiments of the present invention, uplink (UL) controlinformation can be efficiently transmitted in a wireless communicationsystem. In particular, in a situation that a plurality of carriers areaggregated together, control information related to a UL channel can beefficiently transmitted.

According to embodiments of the present invention, the present inventionmay be able to efficiently perform signaling in a carrier aggregationsystem. In particular, the present invention may be able to efficientlysignal a control command for an individual CC and a control command forall CCs in a carrier aggregation system. In more particular, the presentinvention may be able to efficiently transmit channel qualityinformation on a downlink in a carrier aggregation system.

The present invention proposes a method of signaling a control commandfor an individual CC and a control command for all CCs in a systemhaving various CCS exist therein.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram for one example of a structure of a radio frame usedin E-UMTS system.

FIG. 2 is a diagram for one example of a resource grid of a radio frame.

FIG. 3 is a diagram for a structure of a downlink (hereinafterabbreviated DL) subframe.

FIG. 4 is a diagram for one example of a structure of an uplink(hereinafter abbreviated UL) subframe.

FIG. 5 and FIG. 6 are diagrams for examples of CQI creation andtransmission.

FIG. 7 and FIG. 8 are diagrams for examples of a random accessprocedure.

FIG. 9 shows a carrier aggregation (CA) communication system.

FIG. 10 is a diagram for one example of assigning a configurationcommand/information request signal according to one embodiment of thepresent invention.

FIGS. 11 to 15 show examples of transmitting CQI aperiodically accordingto another embodiment of the present invention.

FIG. 16 is a diagram for one example of a base station and a userequipment applicable to the present invention.

BEST MODE FOR INVENTION

First of all, the following descriptions are usable for various wirelessaccess systems including CDMA (code division multiple access), FDMA(frequency division multiple access), TDMA (time division multipleaccess), OFDMA (orthogonal frequency division multiple access), SC-FDMA(single carrier frequency division multiple access) and the like. CDMAcan be implemented by such a radio technology as UTRA (universalterrestrial radio access), CDMA 2000 and the like. TDMA can beimplemented with such a radio technology as GSM/GPRS/EDGE (Global Systemfor Mobile communications)/General Packet Radio Service/Enhanced DataRates for GSM Evolution). OFDMA can be implemented with such a radiotechnology as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,E-UTRA (Evolved UTRA), etc. UTRA is a part of UMTS (Universal MobileTelecommunications System). 3GPP (3rd Generation Partnership Project)LTE (long term evolution) is a part of E-UMTS (Evolved UMTS) that usesE-UTRA. The 3GPP LTE adopts OFDMA in DL and SC-FDMA in UL. And, LTE-A(LTE-Advanced) is an evolved version of 3GPP LTE.

For clarity, the following description mainly concerns 3GPP LTE/LTE-A,by which the present invention may be non-limited.

FIG. 1 is a diagram for one example of a structure of a radio frame usedby E-UMTS system.

Referring to FIG. 1, an E-UMTS system uses a radio frame of 10 ms. And,one radio frame includes 10 subframes. Each of the subframes includes 2slots contiguous with each other. One slot may have a length of 0.5 msand may be constructed with a plurality of symbols (e.g., OFDM(orthogonal frequency division multiplexing) symbols, SC-FDMA (singlecarrier frequency division multiple access) symbols).

FIG. 2 is a diagram for one example of a resource grid of a lot.

Referring to FIG. 2, a slot includes a plurality of OFDM symbols orSC-FDMA symbols and also includes a plurality of resource blocks (RBs)in frequency domain. On resource block includes 12×6 or 12×7 resourceelements (REs). The number N_(RB) of RBs included in a time slot dependson a transmission bandwidth configured in a cell. Each box in theresource grid indicates a minimum resource defined by one symbol and onesubcarrier, which is called a resource element (RE). FIG. 3 exemplarilyshows that a time slot and a resource block include 7 symbols and 12subcarriers, respectively, by which the present invention may benon-limited. For instance, the number of symbols included in a slot maybe variable depending on a length of a cyclic prefix (hereinafterabbreviated CP).

FIG. 3 is a diagram for a structure of a DL subframe.

Referring to FIG. 3, in a DL subframe of LTE system, L1/L2 controlregion and data region are multiplexed together by TDM (time divisionmultiplexing). The L1/L2 control region is configured with 1^(st) n(e.g., 3, 4, etc.) OFDM symbols of a subframe and the rest of the OFDMsymbols are used as the data region. The L1/L2 control region includesPDCCH (physical downlink control channel) configured to carry DL controlinformation and the data region includes PDSCH (physical downlink sharedchannel) as a DL data channel. In order to receive a DL signal, a userequipment reads DL scheduling information from PDCCH and then receivesDL data on PDSCH using resource allocation information indicated by theDL scheduling information. The resource (i.e., PDSCH) scheduled for theuser equipment is allocated by a resource block unit or a resource blockgroup unit.

PDCCH informs a user equipment of information related to resourceallocation of transport channels PCH (paging channel) and DL-SCH(downlink-shared channel), UL scheduling grant, HARQ information and thelike. The information carried on PDCCH is commonly called controlinformation (DCI). In accordance with control information, there arevarious kinds of DCI formats.

Table 1 shows DCI format 0 for UL scheduling.

TABLE 1 Field Bits Comment Format 1 Uplink grant or downlink assignmentHopping flag 1 Frequency hopping on/off RB assignment   7^(a)) Resourceblock assigned for PUSCH MCS 5 Modulation scheme, coding scheme, etc.New Data 1 Toggled for each new transport block Indicator TPC 2 Powercontrol of PUSCH Cyclic shift for 3 Cyclic shift of demodulationreference DMRS signal CQI request 1 To request CQI feedback throughPUSCH RNTI/CRC 16  16 bit RNTI implicitly encoded in CRC Padding 1 Toensure format 0 matches format 1A in size Total 38  — MCS: Modulationand Coding Scheme TPC: Transmit Power Control RNTI: Radio NetworkTemporary Identifier) CRC: Cyclic Redundancy Check

It may be able to identify whether PDCCH s transmitted to a specificuser equipment using RNTI. For instance, assume that PDCCH is CRC maskedwith RNTI named A and that the PDCCH carries UL resource allocationinformation B (e.g., frequency position) and transmission formatinformation C (e.g., transport block size, modulation scheme, codinginformation, etc.). In this case, a user equipment in a cell monitorsPDCCH using RNTI of its own and the user equipment having the RNTI Aperforms a UL transmission in accordance with the informations B and Cobtained from the PDCCH.

FIG. 4 is a diagram for one example of a structure of a UL subframe usedby LTE.

Referring to FIG. 4, a UL frame includes a plurality of slots (e.g., 2slots). Each of the slots may include a different number of SC-FDMAsymbols in accordance with a CP length. The UL subframe may be dividedinto a data region and a control region in frequency domain. The dataregion includes PUSCH and is used to transmit such a data signal as anaudio and the like. The control region includes PUCCH and is used totransmit UL control information (UCI). The PUCCH includes an RB pairsituated at both ends of the data region and performs hopping over theboundary of a slot. The UL control information includes SR (schedulingrequest) to request an uplink resource, HARQ ACK/NACK (hybrid automaticrepeat and request acknowledgement/negative acknowledgement) for DL datapacket, DL channel information and the like. In particular, the DLchannel information may include PMI (precoding matrix indicator), RI(rank indicator) and CQI (channel quality indicator).

Channel Quality Indicator (CQI)

For an efficient communication, it may be necessary to indicate channelinformation by feedback. To this end, DL channel information istransmitted in UL and UL channel information is transmitted in DL. Thischannel information may be called a channel quality indicator(hereinafter abbreviated CQI). The CQI may be created in various ways.In this specification, the CQI may represent channel state information,and more particularly, CQI, PMI, RI or a combination thereof unlessmentioned especially.

For instance, the CQI may be created by one of a method of quantizing achannel state (or, spectrum efficiency) and then indicating thequantized channel state, a method of calculating SINR and thenindicating the calculated SINR, a method of indicating a state ofactually applying a channel like MCS (modulation and coding scheme) andthe like.

Among the CQI generating methods mentioned in the above description, itmay frequently occur that the CQI is crated on the basis of MCS. Thismethod is described in detail as follows. First of all, there is a CQIcreation for a transmission scheme such as HSPDA in 3GPP or the like. Ifthe CAI is created on the basis of the MCS, since the MCS includes amodulation scheme, a coding scheme, a corresponding coding rate and thelike, if the modulation scheme and/or the coding scheme changes, the CQIshould change correspondingly. Hence, at least one CQI is necessary percodeword.

Table 2 shows one example of a case of generating CQI by MCS.

TABLE 2 CQI code rate × index modulation 1024 Efficiency 0 out of range1 QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK 193 0.3770 4 QPSK 308 0.6016 5QPSK 449 0.8770 6 QPSK 602 1.1758 7 16QAM 378 1.4766 8 16QAM 490 1.91419 16QAM 616 2.4063 10 64QAM 466 2.7305 11 64QAM 567 3.3223 12 64QAM 6663.9023 13 64QAM 772 4.5234 14 64QAM 873 5.1152 15 64QAM 948 5.5547

In case that MIMO is applied to a system, the number of the requiredCQIs changes. Since MIMO system generates multi-channels usingmulti-antenna, several codwords are available. Hence, it may benecessary to use several CQIs. In case that a plurality of CQIs areused, a size of corresponding control information proportionallyincreases.

FIG. 5 is a conceptional diagram for one example of CQI creation andtransmission. First of all, a wireless communication system may use linkadaptation in order to use a given channel capacity to the maximum. Thelink adaptation adjusts MCS (modulation and coding scheme) and transmitpower in accordance with a given channel. To this end, a user shouldfeed back channel quality information to a base station eventually.

Referring to FIG. 5, a user equipment measures a DL quality and thenreports a CQI value, which is selected based on the measured DL quality,to a base station on a UL control channel. Subsequently, the basestation performs a DL scheduling (e.g., user equipment selection,resource allocation, etc.) in accordance with the reported CQI value. Inparticular, the CQI value may include one of SINR (Signal toInterference and Noise Ratio), CINR (Carrier to Interference and NoiseRatio), BER (Bit Error Rate) and FER (Frame Error Rate) of a channel ora value resulting from converting one of SINR, CINR, BER and FER to atransmittable data. In case of MIMO system, RI (Rank Information), PMI(Precoding Matrix Information) or the like may be added as informationthat reflects a channel state. For instance, after a user equipment hasobserved time/frequency interval, it may be able to use a largest valueamong CQI indexes shown in Table 2, which meet the following condition,as a CQI value to report in a UL subframe n.

Condition: Transport block error probability does not exceed 0.1 if asingle PDSCH transport block is received via a resource block (CQIreference resource) related to a CQI index with a combination of amodulation scheme corresponding to the CQI index and a transport blocksize.

If a frequency band used by a wireless communication system exceeds acoherence bandwidth, a channel abruptly varies within the correspondingbandwidth. In particular, since a plurality of subcarriers exist withina given bandwidth in a multicarrier system (e.g., OFDM system) and amodulated symbol is carried on each of the subcarriers, it may be ableto transmit a channel on each subcarrier. Hence, in a multicarriersystem using a plurality of subcarriers, a feedback size of channelinformation may increase abruptly. In order to reduce a waste of controlsignal (i.e., control overhead), various methods have been proposed.

In order to reduce the control overhead, a method of decreasing aninformation size of a channel quality indicator is schematicallydescribed as follows.

First of all, it may be able to reduce an information size of a channelquality indicator by changing a channel information transmission unit.For instance, in OFDM system, channel information may be transmitted bya subcarrier group unit instead of a subcarrier unit. If 12 subcarriersare combined together into one subcarrier group in OFDM system using2,048 subcarriers, total 171 subcarrier groups are formed. Hence, a sizeof actually transmitted channel information is reduced down to 171 from2,048.

In this specification, when a frequency band is configured with aplurality of subcarriers like OFDM, if CQI is reported by a subcarrierunit, a basic unit for CQI creation is defined as CQI subcarrier groupor CQI subband. Meanwhile, in case that a frequency band is not dividedinto subcarriers or the like, a whole frequency band is divided intopartial frequency bands and CQI can be then created with reference tothe divided frequency band. In this case, the frequency band divided forthe CQI creation is defined as a CQI subband.

Secondly, by compressing channel information, it may be able to reducean information size of a channel quality indicator. For instance, inOFDM scheme, channel information of each subcarrier is compressed andtransmitted. This compression scheme may include DCT (discrete cosinetransform) for example.

Thirdly, by selecting a frequency band (e.g., CQI subband) forgenerating channel information, it may be able to reduce an informationsize of a channel quality indicator. For instance, instead oftransmitting channel information on all subcarriers in OFDM scheme, itmay be able to use a scheme (i.e., M scheme) of transmitting channelinformation by selecting M subcarriers or M subcarrier groups. Accordingto the M scheme, M frequency bands having best channel quality areselected [Best-M scheme] or M frequency bands preferred by a basestation and/or a user equipment are selected according to a prescribedreason [Preferred-M scheme]. The preferred-M scheme may include thebest-M scheme. When CQI is selected by selecting a frequency band,actually transmitted information can be mainly divided into two parts.In particular, the 1^(st) part is a CQI value part and the 2^(nd) partis a CQI index part. For clarity of the following description, thebest-M scheme is used as a representative example of the M scheme unlessmentioned differently.

FIG. 6 shows a method of generating CQI by selecting CQI subband from afrequency domain. Frequency band selective CQI scheme is mainlyconfigured with 3 parts. First of all, a user equipment selects afrequency band (i.e., CQI subband) to create CQI. Secondly, the userequipment creates and transmits CQI by manipulating channel informationof the selected frequency bands. Thirdly, the user equipment transmitsidentification information (e.g., subband index) on the selectedfrequency band. The above-mentioned parts are discriminated forconvenience, orders of the above-mentioned parts are changeable, and atleast two of the above-mentioned parts may merge into one. Theabove-mentioned parts are described in detail as follows.

The CQI subband selecting method includes a best-M scheme and athreshold-based scheme. The best-M scheme is a scheme of selecting M CQIsubbands in good channel state. According to the best-M scheme, a userequipment selects CQI subbands of indexes #5, #6 and #9 using the best-3scheme. Meanwhile, according to the threshold-based scheme, CQI subbandhaving a channel state higher than a threshold is selected. According tothe threshold-based scheme, a user equipment selects CQI subbands ofindexes #5 and #6 each of which is higher than a threshold.

The CQI value generating and transmitting method includes an individualscheme and an average scheme. In particular, the individual scheme is ascheme of transmitting all CQI values of selected CQI subbands. Hence,according to the individual scheme, if the number of the selected CQIsubbands increases, the number of CQI values to be transmittedincreases. On the other hand, the average scheme transmits an average ofCQI values of the selected CQI subbands. Hence, according to the averagescheme, it is advantageous in that only one CQI value is transmittedirrespective of the number of the selected CQI subbands. Yet, since theaverage scheme transmits a CQI average value of several CQI subbands, itmay have a reduced accuracy. In this case, the average value may includea simple arithmetic average or an average in consideration of channelcapacity.

The CQI subband index transmitting method includes a bitmap index schemeand a general combinatorial scheme. According to the bitmap indexscheme, 1 bit is assigned to each CQI subband. If the corresponding CQIsubband is used, ‘1’ is assigned to the corresponding bit. Otherwise,‘0’ is assigned to the corresponding bit. On the contrary, it may beable to set up a bit value. The bitmap index scheme needs the bit numberamounting to total CQI subbands but may be able to always indicate CQIsubbands via a predetermined number of bit(s) no matter how may CQIsubbands are used. Meanwhile, the combinatorial index scheme determineshow may CQI subbands will be used is determined and then maps everycombination of a predetermined number of CQI subbands selected fromtotal CQI subbands to a corresponding index. In particular, when total NCQI subbands exist, f M CQI subband indexes are used among the N CQIsubbands, a total number of possible combinations can be represented asFormula 1.

$\begin{matrix}{{{}_{}^{}{}_{}^{}} = \frac{{N!}{\left( {N - 1} \right)!}}{M!}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Hence, the bit number to represent the number of cases in accordancewith Formula 12 may be determined by the following expression.

$\begin{matrix}{\left\lceil {\log_{2}\left( {{}_{}^{}{}_{}^{}} \right)} \right\rceil = \left\lceil {\log_{2}\left( \frac{{N!}{\left( {N - 1} \right)!}}{M!} \right)} \right\rceil} & \left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Since the present example relates to a method of selecting 3 CQIsubbands from total 11 CQI subbands, the number of possible cases is 165(i.e., ₁₁C₃=165) and the corresponding bit number is 8 bits(2⁷≦₁₁C₃≦2⁸).

CQI increases the number f transmissions in various dimensions to causemore overhead.

First of all, regarding the increase of a CQI information size in aspace dimension, in case that several codewords are transmitted viaseveral layers in MIMO, several CQIs are necessary. For instance, in3GPP LTE, maximum 2 codewords are available for MIMO and two CQIs arenecessary. When a CQI is configured with 4 bits, if there are 2codewords, total CQIs should be configured with 8 bits. As CQI istransmitted to every user supposed to be informed of a channel state,the increase of a CQI size may occupy most of parts in aspect of wholeradio resources. Therefore, if the increase of the CQI size isminimized, it may be preferable in aspect of channel capacity.

Secondly, regarding the increase of a CQI information size in afrequency dimension, the former CQI mentioned in the above descriptioncorresponds to one frequency band only. If a receiving side notifies aCQI for a frequency band in a best channel state only and a transmittingside performs a service via the corresponding frequency band, CQI isnecessary for one band only. Yet, since the above-described example issuitable for a single user environment but unsuitable for a multi-userenvironment, the demand for a more efficient method rises. A problem,which is caused in the course of scheduling in case of transmitting CQIon one preferred band only, is described in detail as follows. First ofall, if frequency bands preferred by multiple users do not overlap witheach other, there will be no problem. Yet, if several userssimultaneously select a specific frequency band as a best channelenvironment, it may cause a problem that the rest of the users exceptthe user selected by a base station are unable to use the correspondingfrequency band. Hence, if each of the users transmits one preferredfrequency band only, the opportunity for the unselected users to receivea service is basically blocked. In order to solve this problem and toobtain a multi-user diversity gain effectively, CQI transmission forseveral frequency bands is required. In case that CQI corresponding toseveral frequency bands is transmitted, a CQI transmission informationsize is increased by a quantity amounting to a selected frequency band.For instance, after 3 frequency bands have been selected in order of agood channel state, if CQIs and frequency band indicators for theselected 3 frequency bands are transmitted, a CQI transmission sizeincreases three times and an addition transmission for an indicatorindicating a selected frequency band is required.

Thirdly, it may be able to consider an increase of a CQI informationsize (e.g., the number of transmissions) in the dimension that considersboth space and frequency. In particular, several CQIs are necessary forthe space dimension. And, it may consider a case that several CQIs arenecessary for the frequency dimension as well.

Fourthly, an increase of a CQI information size (e.g., the number oftransmissions) may be taken into consideration in other dimensions. Forinstance, if CDMA (code division multiple access) is used, a signalstrength, an interference quantity and the like may fluctuate perspreading code, whereby CQI information is required for each spreadingcode. Hence, it may be able to consider an increase of a CQI informationsize (e.g., the number of transmissions) in code dimension. And, anincrease of a CQI information size in one of various dimensions can betaken into consideration.

In the above description, the cases of requiring several CQIs in variousdimensions are explained. If several CQIs are necessary, it may be ableto introduce the concept of a differential CQI (Delta CQI) to reduce aCQI transmission size. In particular, a reference CQI is normallytransmitted but a difference from a reference CQI is transmitted forother CQIs. When several CQIs are represented by the differentialscheme, the greater number of bits is assigned to a CQI reference valuebut the relatively smaller number of bits is assigned to a differentialvalue, whereby a total transmission size of transmitted CQIs can bereduced.

Table 3 shows UL channel used for CQI transmission in LTE system.

TABLE 3 Periodic CQI Aperiodic CQI Scheduling type transmissiontransmission Frequency non- PUCCH selective Frequency PUCCH PUSCHselective

Referring to Table 3, it may be able to transmit CQI by periodsdetermined by a higher layer using PUCCH. Alternatively, it may be ableto aperiodically transmit CQI using PUSCH if necessary for a scheduler.The case of the transmission on PUSCH is available for the frequencyselective case only. In the following description, CQI transmission isexplained in detail.

1) Aperiodic Transmission of CQI on PUSCH

CQI may be aperiodically transmitted on PUCCH. Aperiodic PUSCH feedbackscheme of CQI is performed in a manner that a base station notifies RBallocation for transmitting feedback information, modulation informationand the like each time using UL grant control information like a normalUL data transmission. CQI may be transmitted on PUSCH individually ortogether with data information. In particular, if a request field is setto 1 in DCI format 0, a user equipment transmits CQI to a base stationusing an allocated PUSCH resource. Meanwhile, if field values of DCIformat 0 meet prescribed conditions, a CQI request-only condition ismet.

Table 4 partially shows DCI format 0 indicating an aperiodic PUSCHfeedback in LTE. If a CQI request field, the number of physical resourceblocks (PRBs) and I_(MCS) indicating an MCS index in DCI format 0 areset to 1, 4 or less and 29, respectively, a user equipment transmits CQIonly on PUSCH without data.

TABLE 4 Value for aperiodic bits PUSCH Feedback RB 7 PRB ≦ 4 assignmentMCS 5 I_(MCS) = 29 CQI request 1 1

Table 5 shows a mode in transmitting CQI on PUSCH. A mode shown in Table5 is selected by a higher layer and all CQIs are transmitted in the samePUSCH subframe.

TABLE 5 PMI Feedback Type Single Multiple No PMI PMI PMI PUSCH WidebandMode 1-2 CQI (wideband CQI) feedback UE Selected Mode 2-0 Mode 2-2 type(subband CQI) Higher Layer- Mode 3-0 Mode 3-1 configured (subband CQI)

2) Aperiodic Transmission of CQI on PUCCH

CQI is periodically transmitted on PUCCH. Yet, if there is a PUSCHtransmission at the timing point of transmitting CQI periodically, theCQI may be transmitted on PUSCH. Table shows a mode in transmitting CQIperiodically. A user equipment creates and transmits CQI by one of theschemes in the modes defined in Table 6.

TABLE 6 PMI Feedback Type Single No PMI PMI PUCCH Wideband Mode 1-0 Mode1-1 CQI (wideband CQI) Feedback UE Selected Mode 2-0 Mode 2-1 Type(subband CQI)

Four kinds of transmission types exist in accordance with transmissioncombinations of CQI PMI and RI.

Type 1: Transmit subband CQI of Mode 2-0 and subband CQI of Mode 2-1

Type 2: Transmit wideband CQI and PMI

Type 3: Transmit RI

Type 4: Transmit wideband CQI

When RI and wideband CQI/PMI are transmitted, they are transmitted insubframes differing from each other in periodicity and offset. If RI andCQI/PMI need to be transmitted in the same frame, the CQI/PMI may not betransmitted.

Uplink Power Control

In a cellular wireless communication system, a user equipment performs atransmission in a manner of raising a power by UL transmit power control(TPC) if a channel environment of a base station is not good. If thechannel environment is good, the user equipment performs a transmissionin a manner of lowering a power. For instance, if the channelenvironment is not good, the base station gives the user equipment a TPCcommand for raising a transmit power. If the channel environment isgood, the base station gives the user equipment a TPC command forlowering a transmit power.

The UL transmission scheme in LTE is characterized in a single carrierproperty using SC-FDMA. In particular, SC-FDMA maintains PAPR (peak toaverage ratio) lower than that of OFDM, thereby enabling a poweramplifier to be efficiently used. For the single carrier property,PUSCH, PUCCH and SRS (sounding reference signal) for UL channelmeasurement are not allowed to be simultaneously transmitted. In casethat data and control signal need to be simultaneously transmitted,information supposed to e transmitted on PUCCH is multiplexed with databy piggyback in PUSCH region. When SRS is transmitted, SC-FDMA symbolfor carrying the SRS is configured not to carry PUSCH or PUCCH. Powercontrols of PUSCH and PUCCH are independently performed.

UL ACK/NACK, which is primary information in uplink, is a response to aDL data reception. Generally, a resource for UL ACK/NACK transmission islinked to a resource used for DL scheduling. Therefore, a PUCCH powercontrol signal including ACK/NACK is transmitted to a user equipment ina manner of being included in a DL control signal indicating DLscheduling information. On the other hand, a PUSCH power control signalis transmitted to a user equipment in a manner of being included in a DLcontrol signal delivering scheduling information on PUSCH.

Random Access Procedure

Scheduling for UL transmission in LTE is enabled only if UL transmissiontiming of a user equipment is synchronized. A random access procedure isused for various usages. For instance, a random access procedure isperformed in case of an initial network access, a handover, a dataoccurrence or the like. A user equipment may be able to obtain ULsynchronization via the random access procedure. Once the ULsynchronization is obtained, a base station may be able to allocate aresource for UL transmission to the corresponding user equipment. Therandom access procedure may be classified into a contention basedprocedure and a non-contention based procedure.

FIG. 7 is a diagram for one example of a contention based random accessprocedure.

Referring to FIG. 7, a user equipment receives information on a randomaccess from a base station via system information. Thereafter, if therandom access is required, the user equipment transmits a random accesspreamble (or a message 1) to the base station [S710]. Once the basestation receives the random access preamble from the user equipment, thebase station sends a random access response message (or, a message 2) tothe user equipment [S720]. In particular, a DL scheduling information onthe random access response message may be transmitted on L1/L2 controlchannel (PDCCH) by being CRC masked with RA-RNTI (random access-RNTI).Having received the RA-RNTI masked DL scheduling signal, the userequipment receives the random access response message on PDSCH and maybe then able to decode the received random access response message.Subsequently, the user equipment checks whether a random access responseinformation indicated to the user equipment is included in the receivedrandom access response message. In doing so, a presence or non-presenceof the random access response information indicated to the userequipment may be checked in a manner of checking whether RAID (randomaccess preamble ID) for the preamble having transmitted by the userequipment is present or not. The random access response information mayinclude a timing advance indicating a timing offset information forsynchronization, a radio resource allocation information on a resourceused in UL, a temporary identifier (e.g., T-RNTI) for user equipment(UE) identification and the like. Once the random access responseinformation is received, the user equipment sends a UL message (or, amessage 3) on UL SCH (uplink shared channel) in accordance with theradio resource allocation information included in the received randomaccess response information [S730]. Having received the UL message fromthe user equipment in the step S730, the base station sends a contentionresolution message (or, a message 4) to the user equipment [S740].

FIG. 8 is a diagram for one example of a non-contention based randomaccess procedure. A non-contention based random access procedure may beused in a handover procedure or may exist if requested by an order givenby a base station. A basic procedure is as good as a contention basedrandom access procedure.

Referring to FIG. 8, a user equipment receives assignment of a randomaccess preamble (i.e., a dedicated random access preamble) for the userequipment only from a base station [S810]. A dedicated random accesspreamble indication information (e.g., a preamble index) may be includedin a handover command message or may be received on PDCCH. The userequipment transmits the dedicated random access preamble to the basestation [S820]. Thereafter, the user equipment receives a random accessresponse from the base station [S830] and the random access procedure isended.

In order to indicate a non-contention based random access procedure witha PDCCH order, DCI format 1A is used. And, the DCI format 1A may be usedfor compact scheduling for one PDSCH codeword. The following informationis transmitted using the DCI format 1A.

-   -   Flag for identifying DCI format 0 or DCI format 1A: This flag is        1-bit flag. A flag value ‘0’ indicates DCI format 0 and a flag        value ‘1’ indicates DCI format 1A.

If all the fields remaining after scrambling CRC of DCI format 1A withC-RNTI are set as follows, the DCI format 1A may be used for a randomaccess procedure according to a PDCCH order.

-   -   Localized/distributed VRB (virtual resource block) assignment        flag: This flag is 1-bit flag. This flag is set to 0.    -   Resource block assignment information: ┌log₂(N_(RB) ^(DL)(N_(RB)        ^(DL))/2┐. Every bit is set to 1.    -   Preamble index: 6 bits    -   PRACH mask index: 4 bits    -   All the remaining bits for compact scheduling of PDSCH in DCI        format 1A are set to 0.

Multiple Component Carriers

In the legacy LTE, 1 component carrier (hereinafter abbreviated CC)exists in each of DL and UL. Since a single DL CC and a single UL CCexist, a TPC command information included in a control signal indicatinga DL scheduling information or a CQI request information included in acontrol signal indicating a UL scheduling information may b recognizedas a control information on a UL CC corresponding to a DL CC.

FIG. 9 shows one example of a carrier aggregation (CA) communicationsystem. LTE-A aggregates a plurality of UL/DL CCs (uplink/downlinkcomponent carriers) to support wider UL/DL bandwidth. The terminology‘component carrier (CC)’ may be substituted with such an equivalentterminology as a carrier, a cell and the like.

Referring to FIG. 9, CCs may be configured adjacent to or non-adjacentfrom each other. A bandwidth of each of the CCs may be determinedindependently. A link between DL CC and UL CC may be configuredsymmetric between a corresponding pair. Moreover, it is possible toconfigure an asymmetric carrier aggregation in which the number of ULCCs and the number of DL CCs are different from each other. Forinstance, if 2 DL CCs and 1 UL CC exist, a configuration in a 2:1correspondence is enabled. The DL CC/UL CC link may be configured in amanner of being fixed to a system. Alternatively, the DL CC/UL CC linkmay be configured semi-statically. PDCCH may b transmitted via a controlregion of each DL CC. The PDCCH may be able to carry information forscheduling PDSCH belonging to the DL CC having the PDCCH belong theretoor information for scheduling PUSCH of the UL CC linked to the DL CC[self-carrier scheduling]. Moreover, the PDCCH may be able to carryinformation for scheduling PDSCH/PUSCH of DL/UL CC in a systemirrespective of the DL CC having the PDCCH belong thereto or the UL CClinked to the corresponding DL CC [cross-carrier scheduling]. In case ofthe cross-carrier scheduling, it may be able to recognize a DL/UL CCbecoming a scheduling target using a carrier indicator (CI). CIinformation is carried on CIF (carrier indicator field) of DCI.Moreover, control information may be configured to be transmitted orreceived on specific CC only. This specific CC may be named a primary CC(or, an anchor CC) and other CCS may be named secondary CCs.

Meanwhile, in case of a carrier aggregation system, since a plurality ofDL CCs are present, it may be necessary to define whether a TPCcommand/CQI request included in a control signal (PDCCH) indicatingDL/UL scheduling information is a control information on an individualCC or information applied to all CCs or a CC group including a pluralityof CCs at a time.

In the following description, a method of efficiently signaling acontrol command for an individual CC and a control command for all CCsin a carrier aggregation system is explained with reference to theaccompanying drawings.

1^(st) Embodiment

When a scheduled CC is designated via CI, the present embodimentproposes that one or more CIF values are additionally configured for atleast one specific CC. In doing so, one of CIF values configured for aspecific CC may be used to assign a configuration command/informationrequest signal for an individual CC and other CIF value may be used toassign configuration command/information request signals for a pluralityof CCs. In this case, the configuration command/information requestsignal may include a TPC command/CQI request and the like. Moreover, aplurality of CCs may become all CCs of a system, all the aggregated CCs,or a specific CC group. If there are two or more CCs having a CIF valueadditionally assigned thereto, a plurality of CCs, to which theconfiguration command/information request signal will be applied, may bedifferent per each of the CC(s) having the CIF value additionallyassigned thereto. The mapping between CIF value and CC index, and the CChaving the CIF value additionally configured therefor may be identicallyconfigured in every user equipment [UE-common configuration] or may beconfigured differently in each user equipment or each user equipmentgroup [UE-specific configuration or UE group-specific configuration].

FIG. 10 is a diagram for one example of assigning a configurationcommand/information request signal according to one embodiment of thepresent invention. In FIG. 10, CCs may be configured adjacent to ornon-adjacent from each other. A bandwidth of each of the CCs may bedetermined independently. Moreover, it is possible to configure anasymmetric carrier aggregation in which the number of UL CCs and thenumber of DL CCs are different from each other.

Referring to FIG. 10, since the total number of CCs is 5, a CI field(CIF) of ┌log₂ 5┐=3 bits are necessary to indicate CI information.According to the present example, CIF values (i.e., 0˜4 (ObOO0, ObOO1,ObO10, ObO11)) represent CC A to CC E in sequence and the CIF value=7(0b111) additionally represents the CC A. According to the presentexample, if CIF value=0˜4, a TPC command or a CQI request may berecognized as a command for an individual CC. If CIF value=7, a TPCcommand or a CQI request is recognized as a command for a plurality ofCCs (e.g., all CCs). According to the present example, in case of aconfiguration command/information request for an individual CC, it maybe necessary to assign a CIF value per each CC. On the contrary, in caseof a configuration command/information request for a plurality of CCs(e.g., all CCs), it may be unnecessary to assign a CIF value per CC. Inparticular, if a configuration command/information request for aplurality of CCs (e.g., all CCs) is transmitted together with schedulinginformation on a specific CC frequently allocated to a user equipment,it may be able to raise field configuration efficiency of a controlsignal for a signal delivery. According to the present example, a TCPcommand/CQI request for all CCs is assigned to only one of the remainingstates. Yet, it may be able to assign a TPC command/CQI request for allCCs or different CC groups to two or more of the remaining states.

When a TPC command or a CQI request is applied to an individual CC, towhich CC the TPC command or the CQI request is applied is described asfollows.

In case that a configuration command is recognized as a command for asingle CC, CC may be designated by the configuration command as follows.

-   -   TPC command for UL CC corresponding to DL CC indicated by a CI        value of PDCCH containing DL scheduling information    -   TPC command for UL CC corresponding to DL CC carrying PDCCH        containing UL scheduling information    -   TPC command for UL CC indicated by a CI value of PDCCH        containing UL scheduling information    -   CQI request for DL CC carrying PDCCH containing UL scheduling        information    -   CQI request for DL CC corresponding to UL CC indicated by a CI        value of PDCCH containing UL scheduling information

In this case, the indication of UL CC via CI may mean that a CI valuedirectly indicates an index of UL CC. Alternatively, the indication ofUL CC via CI may mean that a CI value firstly indicates an index of DLCC and that UL CC corresponding to the DL CC is then indicated.

2^(nd) Embodiment

If a CQI request is made, CQI carried on UL CC may commonly agreed aschannel information on DL CC corresponding to (i.e., linked to) the ULCC by a base station and a user equipment. Yet, there may exist a DL CCwhich is not configured with a linkage to UL CC for any reason(s). Inthis case, such a DL CC may be called a DL CC having not correspondingUL CC or a non-linked DL CC. For instance, if the number of DL CCs isgreater than that of UL CCs, it may be unable to define a 1-to-1 linkagebetween UL CC and DL CC for all DL CCs. If so, since a CQI transmissionfor a non-linked DL CC is not available, the base station needs toinform the user equipment that a CQI for which DL CC needs to betransmitted. The non-linked DL CC may be generated by a DL/UL CC setconfiguration assigned by RRC (radio resource control) signaling for acell deployment or a specific user equipment.

In the following description, a method of indicating a DL CC to which aCQI request is applied, in a situation of an asymmetric carrieraggregation having DL CCs more than UL CCs is explained with referenceto the accompanying drawings. In particular, described is an example ofa method for performing a CQI request for a non-linked DL CC using aPDCCH for scheduling a PUSCH. Although the following description is madein aspect of a user equipment, it is apparent that the same orcorresponding operations may be performed by a base station.

FIG. 11 shows one example of transmitting CQI aperiodically.

Referring to FIG. 11, a user equipment receives a control channelcontaining channel quality information request. In this case, thechannel quality information request may include a CQI request and thecontrol channel may include PDCCH. The channel quality informationrequest may be included in DCI format 0 [S1110]. The user equipment thengenerates channel quality information for at least one specific DLcarrier among a plurality of DL carriers (e.g., DL CCs) [S1120]. In thiscase, the channel quality information may include CQI, PMI, RI or anyone of combinations thereof. Subsequently, the user equipment transmitsthe generated channel quality information via a shared channel [S1130].In this case, the shared channel includes a PDSCH. And, the channelquality information may be transmitted with or without data.

According to the present example, the specific DL carrier in the stepS1120 is indicated using time information related to the channel qualityinformation (or request). In particular, the time information related tothe channel quality information may include time information on a timefor a base station to transmit channel quality information request to auser equipment, time information on a time for a user equipment toreceive channel quality information request from a base station or timeinformation on a time for a user equipment to transmit the generatedchannel quality information to a base station. In particular, accordingto the present example, the time information related to the channelquality information is linked with a DL carrier for which the channelquality information is supposed to be reported. In this case, one timeinformation may be linked with one DL carrier or a plurality of DLcarriers.

In particular, the user equipment may be able to determine DL CC, whichbecomes a CQI report target, using a subframe number (SN) for a basestation to transmit a CQI request, a subframe number for receiving a CQIrequest command from a base station, a system frame number (SFN)corresponding to a corresponding subframe number, or a combination (SSN)of a corresponding subframe number and a system frame number (SFN). And,the user equipment may be able to determine DL CC, which becomes a CQIreport target, using a subframe number, a system frame number, or acombination (SSN) of a subframe number and a system frame number fortransmitting a CQI report. In case of LTE, a subframe index fortransmitting a CQI is equal to a sum resulting from adding 4 to asubframe index for receiving a CQI request [i.e., CQI transmittedsubframe index=(CQI request received subframe index) to 4], by which thepresent example may be non-limited. Alternatively, SSN may given as aform that contains ‘A*SFN+B*SN’ (where, A and B are integers equal o orgreater than 0). And, the system frame number may be corresponding to aradio frame number.

For example, when a user equipment aggregates total NC DL CCs, if a CQIrequest command is received, the user equipment may recognize DL CC,which is linked with an output value of Formula 3, as a CQI reporttarget.

modulo(SN,NC),modulo(SFN,NC),or modulo(SSN,NC)  [Formula 3]

In Formula 3, modulo(X, Y) is a function of returning a remainderresulting from dividing X by Y. And, NC, SN, SFN and SSN are same asdefined in the forgoing description.

In particular, a user equipment may be able to recognize DL CC, whichhas an output of Formula 3 as a CC index, as a CQI report target. And,the user equipment may be able to recognize DL CC, which has a CC indexcorresponding to a value obtained using an output value of Formula 3, asa CQI report target. In this case, the DL CC index may be determined inadvance by broadcast/RRC signaling and the like.

This method may be applicable to all DL CCs irrespective of whether DLCC is configured to correspond to UL CC (i.e., whether DL CC is linkedto UL CC in advance) or not. A DL CC set, to which the present method isapplied, includes all DL CCs assigned to a user equipment or a portionof DL CCs designated by higher layer signaling (e.g., RRC signaling,etc.) only.

FIG. 12 shows one example of linking time information related to CQI(request) in the method shown in FIG. 11 to DL CC(s) of CQI reporttarget.

Referring to FIG. 12, when a non-linked DL CC exists, a CQI linkage maybe configured to enable a CQI request command to be recognized as a CQIrequest command for a plurality of DL CCs. For instance, Formula 3 maybe modified into the following formula.

modulo(SN,NC+N),modulo(SFN,NC+N),or modulo(SSN,NC+N)  [Formula 4]

In Formula 4, modulo(X, Y) is a function of returning a remainderresulting from dividing X by Y. And, NC, SN, SFN and SSN are same asdefined in the forgoing description. Moreover, N is an integer equal toor greater than 0.

Referring to Formula 4, an output value of modulo function has a valueof 0˜(NC+N−1). In this case, the output value of 0˜(NC−1) (e.g., 0, 1,2) is used to recognize an individual DL CC as a CQI report target. And,an output value of NC˜(NC+N−1) (e.g., 3, 4) may be used to recognize aplurality of DL CCs as a CQI report target. In this case, a plurality ofthe DL CCs may include a full DL CC set, an aggregated DL CC set, and anon-linked DL CC set.

Alternatively, Formula 3 may be modified into the following formula.

modulo(SN,NC−N),modulo(SFN,NC−N),or modulo(SSN,NC−N)  [Formula 5]

In Formula 5, modulo(X, Y) is a function of returning a remainderresulting from dividing X by Y. And, NC, SN, SFN and SSN are same asdefined in the forgoing description. Moreover, N is an integer equal toor greater than 0.

Referring to Formula 5, an output value of modulo function has a valueof 0˜(NC−N−1). Since the number of output values is smaller than thenumber of aggregated carriers, a portion of the output values may beoverlappedly mapped to a plurality of DL CCs. Hence, a portion of theoutput values (e.g., 1, 2, 3) is used to recognize an individual DL CCas a CQI report target. And, the rest of the output value (e.g., 0) maybe used to recognize a plurality of DL CCs as a CQI report target.

FIG. 11 and FIG. 12 show the time information related to CQI (request)to determine DL CC becoming a CQI report target, for clarity of thedescription of the invention. Optionally, it may be able to determine DLCC becoming a CQI report target using another parameter related tocarrier aggregation in addition. For instance, in order to determine DLCC becoming a CQI report target, a DL CC index (CIF) for receiving a CQIrequest command or a UL CC index (CIF) for transmitting CQI may be usedtogether. For instance, the corresponding DL CC index (CIF) or thecorresponding UL CC index (CIF) may be used as an offset value.

FIG. 13 shows another example of transmitting CQI aperiodically.

Referring to FIG. 13, when a non-linked DL CC exists, if a CQI requestis received, it may be able to configure a CQI linkage so as to enablethe CQI request to be recognized as a CQI request for a plurality of DLCCs. For instance, if DL CC #1/#2 is linked with UL CC #1/#2 and DL CC#3/#4/#5 is a non-linked DL CC, it may be able to configure a CQIlinkage such that, in view of CQI transmission, the DL CC #3 and the DLCC #4/#5 are linked to the UL CC #1 and the UL CC #2, respectively.Hence, if a user equipment needs to transmit CQI on UL CC #1 in responseto a CQI request, the user equipment recognizes both of the DL CC #1 andthe DL CC #3 as CQI report targets and then performs CQI feedback.Similarly, if a user equipment needs to transmit CQI on UL CC #2 inresponse to a CQI request, the user equipment recognizes all the DL CCs#1, DL CC #4 and DL CC #5 as CQI report targets and then performs CQIfeedback. In this case, the CQI linkage may be pre-determined in advancevia broadcast/RRC signaling or the like. And, a plurality of DL CCs (forclarity, named a CQI CC set) having CQI request command applied theretomay include one non-linked DL CC, a portion of non-linked DL CCs, or allnon-linked DL CCs. The present example corresponds to a case that twoCQI CC sets are configured. In accordance with an example ofimplementation, a CQI request command may apply to all DL CCs in a CQICC set [i.e., Case 1] or a portion of DL CCs in a CQI CC set [i.e., Case2]. Case 2 may be performed using the former method described withreference to FIG. 10 and FIG. 11, by which the example may benon-limited.

FIG. 14 shows another example of transmitting CQI aperiodically.

Referring to FIG. 14, a plurality of CIF values respectively indicatingdifferent DL CC indexes may overlap to indicate the same UL CC index.According to this method, if a plurality of CIF values in PDCCHsscheduling PUSCH to carry CQI are configured to indicate the same UL CC,it may be able to discriminate DL CCs, which become CQI report targets,using a plurality of different CIF values indicating the same UL CC. Forinstance, referring to FIG. 14, assume that 5 DL CCs and 2 UL CCs exist,that DL CC #1 and DL CC #2 correspond to UL CC #1 and UL CC #2,respectively, and that there is no UL CC(s) configured to correspond toDL CC #3, DL CC #4 and DL CC #5. On this assumption, CIF valuesindicating DL CC #1, DL CC #3 and DL CC #5, which correspond toodd-numbered indexes, may be configured to commonly indicate UL CC #1.And, CIF values indicating DL CC #2 and DL CC #4, which correspond toeven-numbered indexes, may be configured to commonly indicate UL CC #2.Hence, if a user equipment receives a CQI request via a UL grant PDCCHset to ‘CIF=0b010’, a CQI for DL CC (i.e., DL CC #3) corresponding to‘CIF=0b010’ is transmitted on UL CC (i.e., UL CC #1) corresponding to‘CIF=0b010’. Information on a CIF value having DL/UL CC indexes mappedthereto overlappedly may be defined through specific rule/functionconfigured in advance between a base station and a user equipment or maybe notified to a user equipment by a base station through RRC or L1/L2signaling.

FIG. 15 shows another example of transmitting CQI aperiodically.

Referring to FIG. 15, a user equipment receives a control channelcontaining channel quality information request. In this case, thechannel quality information request may include a CQI request and thecontrol channel may include PDCCH. The channel quality informationrequest may be included in DCI format 0 [S1510]. The user equipment thengenerates channel quality information on at least one specific DLcarrier among a plurality of DL carriers (e.g., DL CCs) [S1520]. In thiscase, the channel quality information may include CQI, PMI, RI or one ofcombinations thereof. Subsequently, the user equipment transmits thegenerated channel quality information via a shared channel [S1530]. Inthis case, the shared channel includes a PDSCH. And, the channel qualityinformation may be transmitted with or without data.

According to the present example, DL carrier becoming a CQI reporttarget is determined depending on whether a CQI request only conditionis met. In particular, according to this method, depending on whetherfield value(s) configuring a UL PUSCH grant PDCCH, of which CQI requestcommand is activated (i.e., a CQI request bit is set to 1), meets aspecific condition or not, a DL CC becoming a CQI report target may bedifferently indicated/recognized. For instance, if the field value(s)configuring PDCCH meets a condition ‘CQI request only’ (i.e., acondition for enabling a scheduled PUSCH to carry a CQI only without ULdata (i.e., transport block for UL-SCH)), a user equipment may be ableto indicate/recognize that a CQI only for a DL CC linked to a UL CC, onwhich PUSCH will be transmitted, is reported. On the contrary, if thecorresponding field value(s) in the UL PUSCH grant PDCCH, of which CQIrequest command is activated, does not meet the condition ‘CQI requestonly, the user equipment may report CQI for all DL CCs assigned to theuser equipment or may indicate/recognize that CQI for DL CC grouppreviously designated to UL CC, which will carry PUSCH, is reported [Alt1]. In this case, the condition ‘CQI request only’ may include ‘CQIrequest bit=1’, ‘I_(MCS)=29’, and ‘number of RBs for PUSCH transmissionis equal to or smaller than 4 (i.e., N_(RB)≦4)’ [cf. Table 4].Alternatively, the condition ‘CQI request only’ may include a conditionnewly defined in LTE-A. The proposal Alt 1 may be more suitable for acase that an upper limit of N_(RB) (or, upper and lower limits ofN_(RB)) for the condition ‘CQI request only’ is defined relativelysmall.

If the upper limit of N_(RB) (or, upper and lower limits of N_(RB)) forthe condition ‘CQI request only’ is defined relatively large in LTE-A,an operation opposite to the method Alt 1 may be more appropriate. Forinstance, if field value(s) configuring a UL PUSCH grant PDCCH(indicating a CQI request command) meets the condition ‘CQI requestonly’, it may be indicated/recognized that all CQIs for all DL CCsassigned to a user equipment or all CQIs for DL CC group previouslydesignated to UL CC, on which PUSCH will be transmitted, are reported.On the contrary, if the corresponding field value(s) in the CQI requestcommand activated UL PUSCH grant PDCCH does not meet the condition ‘CQIrequest only’, it may be indicated/recognized that CQI only for the DLCC linked to the UL CC, on which PUSCH will be transmitted is, reported[Alt 2]. Meanwhile, it may be possible to configure whether to apply theproposal Alt 1 or the proposal Alt 2 cell-specifically orUE-specifically (or, UE group-specifically).

3^(rd) Embodiment

If UL timing synchronization is independently controlled per UL CC for auser equipment to which a plurality of UL CCs are assigned, a basestation should independently adjust UL timing advance for each UL CC ofthe user equipment per UL CC. To this end, the base station should beable to give a command for RACH preamble transmission independently perUL CC using the former PDCCH order described with reference to FIG. 8.Meanwhile, due to some reasons, limitation may be put on DL CC on whichthe PDCCH order for initiating a random access can be carried. This maycorrespond to an asymmetric carrier aggregation situation in which thenumber of UL CCs is greater than that of DL CCs. Moreover, the PDCCHorder for initiating a random access may be carried on specific DL CC(e.g., Primary CC) only due to such a reason as overhead reduction andthe like. Hence, in order to indicate an RACH preamble transmission fora specific UL CC using a PDCCH order carried on one DL CC, it may benecessary to give the PDCCH order to inform on which UL CC a userequipment will transmit RACH preamble.

Therefore, the present embodiment proposes a method of configuring a CIFvalue, which is provided for a PDCCH order for performing an RACHpreamble transmission command for UL CC, to directly indicate an indexof UL CC on which a user equipment will transmit an RACH preamble. Forinstance, if an RACH preamble transmission command is transmitted usingDCI format 1A, if each field in DCI format 1A is set to a PDCCH orderfor a random access, a user equipment may interpret a CIF value of thecorresponding PDCCH as an index of UL CC on which an RACH preamble willbe transmitted. Alternatively, it may be able to consider anothermethod. Namely, a CIF value in PDCCH order is indicated by a DL CCindex. And, a UL CC to carry an RACH preamble is interpreted as a UL CCcorresponding to a corresponding DL CC. As mentioned in the foregoingdescription with reference to FIG. 14, it may be able to use CIF valuesconfigured to have DL/UL CC indexes mapped duplicatively.

FIG. 16 is a diagram for one example of a base station and a userequipment applicable to the present invention.

Referring to FIG. 16, a wireless communication system may include a basestation (BS) 110 and a user equipment (UE) 120. In DL, a transmitter isa part of the bas station 110 and a receiver is a part of the userequipment 120. In UL, a transmitter is a part of the user equipment 120and a receiver is a part of the base station 110. The base station 110may include a processor 112, a memory 114 and a radio frequency (RF)unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present invention. The memory114 is connected with the processor 112 to store various kindsinformations related to operations of the processor 112. The RF unit 116is connected with the processor 112 and then transmits and/or receivesradio signals. The user equipment 120 may include a processor 122, amemory 124 and a radio frequency (RF) unit 126. The processor 122 may beconfigured to implement the procedures and/or methods proposed by thepresent invention. The memory 124 is connected with the processor 122 tostore various kinds informations related to operations of the processor122. The RF unit 126 is connected with the processor 122 and thentransmits and/or receives radio signals. The base station 110 and/or theuser equipment 120 may have a single antenna or multiple antennas.Besides, the user equipment 120 may further include at least one of apower management module, a battery, a display, a keypad, a SIM card(optional), a speaker and a microphone [not shown in the drawing].

The above-described embodiments may correspond to combinations ofelements and features of the present invention in prescribed forms. And,it may be able to consider that the respective elements or features maybe selective unless they are explicitly mentioned. Each of the elementsor features may be implemented in a form failing to be combined withother elements or features. Moreover, it may be able to implement anembodiment of the present invention by combining elements and/orfeatures together in part. A sequence of operations explained for eachembodiment of the present invention may be modified. Some configurationsor features of one embodiment may be included in another embodiment orcan be substituted for corresponding configurations or features ofanother embodiment. And, it is apparently understandable that a newembodiment may be configured by combining claims failing to haverelation of explicit citation in the appended claims together or may beincluded as new claims by amendment after filing an application.

In this disclosure, embodiments of the present invention are describedcentering on the data transmission/reception relations between a basestation and a user equipment. In this disclosure, a specific operationexplained as performed by a base station may be performed by an uppernode of the base station in some cases. In particular, in a networkconstructed with a plurality of network nodes including a base station,it is apparent that various operations performed for communication witha user equipment may be performed by a base station or other networks(e.g., relay, etc.) except the base station. In this case, ‘basestation’ can be replaced by such a terminology as a fixed station, aNode B, an eNode B (eNB), an access point and the like. And, ‘terminal’may be replaced by such a terminology as a user equipment (UE), a mobilestation (MS), a mobile subscriber station (MSS)’ and the like.

Embodiments of the present invention may be implemented using variousmeans. For instance, embodiments of the present invention may beimplemented using hardware, firmware, software and/or any combinationsthereof. In case of the implementation by hardware, one embodiment ofthe present invention may be implemented by one of ASICs (applicationspecific integrated circuits), DSPs (digital signal processors), DSPDs(digital signal processing devices), PLDs (programmable logic devices),FPGAs (field programmable gate arrays), processor, controller,microcontroller, microprocessor and the like.

In case of the implementation by firmware or software, one embodiment ofthe present invention may be implemented by modules, procedures, and/orfunctions for performing the above-explained functions or operations.Software code may be stored in a memory unit and may be then drivable bya processor. The memory unit may be provided within or outside theprocessor to exchange data with the processor through the various meansknown to the public.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents. For instance, therespective configurations disclosed in the aforesaid embodiments of thepresent invention can be used by those skilled in the art in a manner ofbeing combined with one another. Therefore, the present invention isnon-limited by the embodiments disclosed herein but intends to give abroadest scope matching the principles and new features disclosedherein.

INDUSTRIAL APPLICABILITY

Accordingly, the present invention is applicable to wireless accesssystems. In particular, the present invention is applicable to a methodand apparatus for transmitting channel quality information in a wirelesscommunication system.

1. A method of transmitting channel quality information, which istransmitted by a user equipment in a wireless communication system usingmultiple carriers, the method comprising: receiving a control channelincluding channel quality information request; generating the channelquality information on at least one specific DL carrier among aplurality of DL carriers after receiving the control channel; andtransmitting the channel quality information via a shared channel,wherein the at least one specific DL carrier is indicated using timeinformation related to a reception of the channel quality informationrequest or a transmission of the channel quality information.
 2. Themethod of claim 1, wherein the time information related to the receptionof the channel quality information comprises a subframe number, a systemframe number or a combination thereof, for a base station to transmitthe channel quality information request or for the user equipment toreceive the channel quality information request.
 3. The method of claim1, wherein the time information related to the transmission of thechannel quality information comprises a subframe number, a system framenumber or a combination thereof, for the user equipment to transmit thechannel quality information.
 4. The method of claim 1, wherein an indexindicating the at least one specific DL carrier is linked with modulo(X, Y), wherein the X is an index associated with the time information,wherein the Y is the number of aggregated carriers, and wherein themodulo (X, Y) indicates a remainder resulting from dividing the X by theY.
 5. The method of claim 1, wherein the channel quality informationcomprises at least one of CQI (Channel Quality Indicator), PMI(Precoding Matrix Indicator) and RI (Rank Indicator).
 6. The method ofclaim 1, wherein the control channel further comprises carrierindication information.
 7. The method of claim 1, wherein the controlchannel comprises a PDCCH (Physical Downlink Control Channel) andwherein the shared channel comprises a PDSCH (Physical Downlink SharedChannel).
 8. A user equipment, which is configured to transmit channelquality information in a wireless communication system using multiplecarriers, comprising: an RF (radio frequency) unit; and a processorconfigured to receive a control channel including channel qualityinformation request, the processor configured to create the channelquality information on at least one specific DL carrier among aplurality of DL carriers after receiving the control channel, theprocessor configured to transmit the channel quality information via ashared channel, wherein the at least one specific DL carrier isindicated using time information related to a reception of the channelquality information request or a transmission of the channel qualityinformation.
 9. The user equipment of claim 8, wherein the timeinformation related to the reception of the channel quality informationcomprises a subframe number, a system frame number or a combinationthereof, for a base station to transmit the channel quality informationrequest or for the user equipment to receive the channel qualityinformation request.
 10. The user equipment of claim 8, wherein the timeinformation related to the transmission of the channel qualityinformation comprises a subframe number, a system frame number or acombination thereof, for the user equipment to transmit the channelquality information.
 11. The user equipment of claim 8, wherein an indexindicating the at least one specific DL carrier is linked with modulo(X, Y), wherein the X is an index associated with the time information,wherein the Y is the number of aggregated carriers, and wherein themodulo (X, Y) indicates a remainder resulting from dividing the X by theY.
 12. The user equipment of claim 8, wherein the channel qualityinformation comprises at least one of CQI (Channel Quality Indicator),PMI (Precoding Matrix Indicator) and RI (Rank Indicator).
 13. The userequipment of claim 8, wherein the control channel further comprisescarrier indication information.
 14. The user equipment of claim 8,wherein the control channel comprises a PDCCH (Physical Downlink ControlChannel) and wherein the shared channel comprises a PDSCH (PhysicalDownlink Shared Channel).